This invention relates in general to breath testing devices and in particular to a new and useful apparatus and method for determining the alcohol content of exhaled air.
Breath alcohol testers must be easy to carry by the user and be able to be applied immediately. The test result should be sufficiently accurate, despite the often adverse circumstances under which the test must be performed, also in the open. The often lacking willingness of the test person to cooperate must not affect the test result.
In one known breath alcohol tester the test person blows directly through a test tube via a mouthpiece. The parameter "exhaled amount of gas", required to determine the alcohol concentration in the exhaled air, is found by means of a measuring bag which follows the test tube and must be inflated. This known method required test tubes of low resistance to keep the blowing effort of the test person within limits. Therefore, the breath alcohol test tubes must be of relatively large section and can have a relatively short preparation layer only. Since the length of discoloration of the reagent preparation is the measure of the alcohol content in the exhaled air, a prolongation would be in the sense of a greater measuring sensitivity, (DE-PS No. 10 52 630).
One known device to measure the exhaled gas mixture by means of a breath alcohol test tube has a breath sampling chamber of a defined maximum volume. It is brought, by the breath blown in, from a starting position into an end position so that it contains a breath sample of a defined volume. When the breath sampling chamber is filled, a pump is actuated which conducts the breath contained in the breath sampling chamber to and through the breath alcohol test tube via a line. Conducting the breath through the breath sampling chamber leads to difficulties on account of cooling. To prevent this, the entire device, not only the chamber but also all lines, is heated. This makes the device complicated, bulky and, fundamentally, requires the warm-up period before use (DE-PS No. 12 98 311).
The length of discoloration being the measure of the alcohol content in the exhaled air, lengthening it would produce a greater measuring sensitivity. The test tube employed to analyze the air at work stations are used in conjunction with a gas sensing pump. With it, greater flow resistances in the test tube can be overcome. These standard test tubes are of smaller diameter, from which then follows a longer reagent length, which is totally in the sense of the desired extension of the discoloration.